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Concept
Grenville orogeny
Summary
The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico, as well as to Scotland.
Grenville orogenic crust of mid-late Mesoproterozoic age (c. 1250–980 Ma) is found worldwide, but generally only events which occurred on the southern and eastern margins of Laurentia are recognized under the "Grenville" name.
These orogenic events are also known as the Kibaran orogeny in Africa and the Dalslandian orogeny in Western Europe.
The problem of timing the Grenville orogeny is an area of some contention today. The timescale outlined by Toby Rivers in 2002 is derived from the well-preserved Grenville Province and represents one of the most detailed records of the orogeny. This classification considers the classical Grenville designation to cover two separate orogenic cycles; the Rigolet, Ottawan and Shawingian orogenies compose the Grenville Cycle, and the Elzevirian orogeny stands on its own. Due to the great size of the area affected by Grenville events, there is some variance in timing across the orogenic belt. Regional variations below discusses local deviations from Rivers' timeline, presented here.
Ages are approximated from the magmatic activity associated with the individual cycles of the orogeny. The gaps in the ages of the compression cycles and isotope analysis of hornblende, biotite, and potassium feldspar suggest that extension was occurring when compression had momentarily ceased.
Rivers' 2008 paper has now examined the timing of the different periods of the orogeny and reconstructed the timeline based on the spatial and temporal metamorphism of the rocks present. According to this newer version of the timeline which is a composite of Rivers 1997 and Gower and Krogh 2002, the Elzevirian orogeny occurs from 1240 to 1220 Ma, the Shawinigan occurs from 1190 to 1140 Ma and is no longer part of the Grenville cycle, the Ottawan (now 1090–1020 Ma) and Rigolet (still 1010–980 Ma) become phases which are grouped into the Grenvillian orogeny.
Official source
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